Skip to content
Crucible Fit
  • The Crucible
  • The Week
  • Programs
  • Train Your Way
  • Pricing
Get Crucible
  • The Crucible
  • The Week
  • Programs
  • Train Your Way
  • Apple Watch
  • Pricing
  • FAQ
  • Training Guides
Get Crucible
Crucible Fit

A daily functional fitness test for iPhone, Apple Watch and Android. Stations, reps and the Crux, sized to your readiness and your kit.

Download on the App StoreGet it on Google Play

Crucible Fit

  • The Crucible
  • The Week
  • Programs
  • Train Your Way
  • Apple Watch
  • Pricing

Explore

  • Training Guides
  • Exercise Library
  • FAQ
  • Press
  • Support

Legal

  • Terms and Conditions
  • Privacy Policy
  • Consumer Health Data Notice

CRUCIBLE FIT™ and Crux by Crucible Fit are trademarks of Crucible Fit, LLC.

© 2026 Crucible Fit, LLC. All rights reserved. Apple, the Apple logo, iPhone and Apple Watch are trademarks of Apple Inc., registered in the U.S. and other countries. App Store is a service mark of Apple Inc. Google Play and the Google Play logo are trademarks of Google LLC.

  1. Home
  2. /
  3. Exercises
  4. /
  5. Core & Abs
  6. /
  7. Kneeling Knee Tap To Crossed Reach

Exercise guide

Kneeling Knee Tap To Crossed Reach

  • Intermediate
  • Compound
  • Rep-based
  • Waist

This dynamic stability exercise integrates the posterior chain and anterior core, using a cross-body pattern to challenge the obliques and improve spinal control. It effectively builds functional core strength by requiring the body to maintain balance while moving opposite limbs.

Reviewed by the Crucible Fit team · Updated June 2026

Watch the Kneeling Knee Tap To Crossed Reach demonstrationVideo and instructions for every movement are in the Crucible Fit app.

Muscles worked

Primary

  • Abs
  • Obliques

Secondary

  • Erector spinae

Equipment

  • Body weight

Setup

  1. Begin in a quadruped position on all fours with your hands directly under your shoulders and knees under your hips.
  2. Engage your core to create a flat, neutral spine from head to tailbone.
  3. Distribute your weight evenly across your palms and the tops of your feet.

How to do it

  1. Simultaneously lift your right arm and left leg until they are fully extended and parallel to the floor.
  2. Exhale and crunch your midsection to bring your right hand and left knee together under your torso, tapping the knee with your hand.
  3. Inhale as you extend back out, reaching your arm and leg slightly across the midline of your body to emphasize the obliques.
  4. Return to the starting position with control and repeat the sequence on the opposite side, alternating for the duration of the set.

Form checklist

  • Keep your hips square to the floor; do not let them tilt or rotate during the reach.
  • Maintain a neutral neck by gazing at the floor about six inches in front of your hands.
  • Avoid arching your lower back when extending the leg; focus on glute contraction instead.
  • Keep the supporting shoulder 'packed' by pushing the floor away actively.

Pro tips

  • To maximize oblique engagement, focus on the 'crunch' phase by actively pulling your belly button toward your spine as the knee and hand meet.
  • Slow the tempo down to a 3-second extension to remove momentum and force the stabilizer muscles to work harder.
  • Imagine a glass of water resting on your lower back that you must not spill throughout the entire movement.

Make it harder

  • Perform the movement from a high plank position (knees off the floor) to drastically increase the balance and core demand.
  • Hold a light dumbbell in the reaching hand or wear ankle weights to increase the resistance on the glutes and shoulders.

Frequently asked

What muscles does the kneeling knee tap to crossed reach work?
The kneeling knee tap to crossed reach primarily targets the abs and obliques, and also works the erector spinae as secondary muscles.
What equipment do you need for the kneeling knee tap to crossed reach?
The kneeling knee tap to crossed reach requires no equipment — just your body weight.
Is the kneeling knee tap to crossed reach good for beginners?
The kneeling knee tap to crossed reach is rated intermediate. Build a base with simpler variations first, then progress to it with light load and strict form.

Related exercises

  • 3/4 Sit-UpBeginner · abs and obliques
  • 45 Degree Bicycle Twisting CrunchIntermediate · abs and obliques
  • 45 Degree Lean Back Alternate Knee RaiseBeginner · abs and obliques
  • 45 Degrees Arms PlankIntermediate · abs, deltoids, obliques, and pectorals

Train it with Crucible Fit.

Every movement in this library is in the app with video and instructions, ready for your own sessions on the days between Crucibles. Your first Crucible is on us.

Download on the App StoreGet it on Google Play

See how a Crucible works